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Old 06-10-2018, 01:44 PM   #1
drr
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Piers under slab questions/concerns


I'm on my first build and I'm a bit worried about things not going right. My foundation is to be a structural slab of 'waffle' design (concrete grade beams running in crisscross patterns under the entire slab) and has about 60 piers in various places under the concrete beams for support. The piers are poured and the trenches for the beams are being dug at the moment. My concerns are:

The foundation plan calls for the piers to not be attached to the slab grade beams, only for it to rest on them. However, many of the beam had one or two rebar sticking out the top which has simply been hammered over so that is lays sideways along the top of the piers. Is this sufficient to abide by the foundation design of not extending the pier reinforcement into the grade beams? The piers also have very bulbous rough tops that would seems to interlock with the grade beams somewhat even without rebar.

The piers are not all the same height coming out of the grade beam trenches and the foundation plan calls for the grade beams to be 12" wide and 24" high. If piers differ in hieght by 6", I would think the correct thing to do would be to make the grade beams 24" high from the TALLEST pier, therefore, necessitating that in some places the grade beams may be 30" or so, but no less thick (height) than 24". Is this right? I am worried that instead I will have grade beams that are only 18" high in some spots where the pier extends up into the grade beam trench. Would this be okay or is this bad?

Next, many of the piers are not centered in the grade beam trenches. Some exterior corners have the corner extended out a bit and rounded out around a pier that wasn't centered in the corner. The slab is not supposed to go out that far, but can the grade beams extend out further under the edge of the slab to utilize the ill placed pier without causing issues with where the slab is supposed to end?

Similarly, there are some piers along a grade beam length that are not centered and instead only 1/2 of the pier is in the trench. They carved out the dirt around the other 1/2 of the pier to incorporate the entire pier but this doesn't seem to be right. The grade beam is really only resting on 1/2 the pier if you look at the entire length's width of the grade beam every else except where they widened it right above the pier. Will the pier still give it's intended support to the grade beam in situations like this?

I'm just looking for some reassurance that this is typical and okay or, conversely, that I should be concerned and need to speak up before more forming continues.
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Old 06-10-2018, 02:25 PM   #2
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Re: Piers under slab questions/concerns


Here's 4 pics showing an off corner pier, piers not centered along a grade beam trenches, and a pier that is much taller than other piers in the grade beam trench (and has a mountainous non flat top worse than many).








Last edited by drr; 06-10-2018 at 02:28 PM.
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Old 06-10-2018, 03:10 PM   #3
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Re: Piers under slab questions/concerns


Here's a pic with an example of how the rebar extending out of the piers (only some have it extending out) was treated I suppose to satisfy the requirement that the pier reinforcement not extend into the grade beams. Is this adequate? or should rebar be cut and removed?



The rebar placement in these piers was kind of all over the place to--literally. Maybe this is okay as long as 2 bars (as specified) got in there?











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